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Golf club shaftRelated Patent Categories: Games Using Tangible Projectile, Golf, Club Or Club Support, Shaft, Including Nonmetallic Material Or Vibratory Wave Modifying FeatureGolf club shaft description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070032310, Golf club shaft. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This nonprovisional application claims priority under 35 U.S.C. .sctn.119(a) on Patent Application No(s). 2005-223847 filed in Japan on Aug. 2, 2005, the entire contents of which are hereby incorporated by reference. FIELD OF THE INVENTION [0002] The present invention relates to a golf club shaft made of a fiber reinforced resin. More particularly, the present invention is intended to improve the strength of a golf club shaft by improving a matrix resin composing the golf club shaft. DESCRIPTION OF THE RELATED ART [0003] In recent years, to allow golfers to hit golf balls at high speeds and stably in flight distances, the present tendency is to make a weight concentrate in a golf club head and make the golf club shaft as lightweight as possible. Therefore as the material of the golf club shaft, the fiber reinforced resin such as a carbon prepreg that is lightweight and has a high specific strength and specific rigidity is mainly used. [0004] Owing to a low birth rate, there is a tendency for senior golfers to increase in the future. Thus there is a growing demand for the development of a golf club suitable for senior golfers. Because seniors are powerless, the golf club for them is demanded to be lightweight and have a high head speed so that flight distances of golf balls are constant. To increase the head speed, it is necessary to make the shaft soft and flexible. To this end, methods of decreasing the number of fiber layers of the shaft made of the fiber reinforced resin, decreasing the modulus of elasticity of fibers, and differentiating fiber angles from each other are conventionally used. But shafts manufactured by using these methods have a low strength. Thus it is difficult to manufacture a shaft having a light weight, a high flexibility, and a high strength. [0005] To overcome the above-described problem, there are proposed golf club shafts as disclosed in Japanese Patent Application Laid-Open Nos. 2004-298357 (patent document 1) and 2004-188191 (patent document 2). In these patent documents, at least one part of the fiber reinforced resin layers composing the shaft contains the carbon nano-tube. According to the description made in the specification of the patent documents, the shaft is allowed to have a restrained bending rigidity, a light weight, and a high strength. [0006] The carbon nano-tube is a faultless single layer tubular material formed by cylindrically rounding a flat hexagonal net of graphite or a multi-layer tubular material composed of hexagonal nets of graphite layered one upon another in a telescopic system. The carbon nano-tube is a superfine carbon fiber having a diameter in the range of 1 nm to 100 nm and has mechanical properties superior to conventional carbon fiber in its torsional strength and bending strength. [0007] Because the carbon nano-tubes are cylindrical, they have a low fluidity and are liable to aggregate with one another. To make the sizes (longitudinal length) of the carbon nano-tubes equal to each other, it is necessary to precisely control arc discharge to be performed between carbon electrodes in manufacturing the carbon nano-tubes. It is difficult to manufacture the carbon nano-tubes having a uniform size. Therefore variations are liable to occur in the strength distribution of the fiber reinforced resin containing the carbon nano-tubes. [0008] Patent document 1: Japanese Patent Application Laid-Open No. 2004-298357 [0009] Patent document 2: Japanese Patent Application Laid-Open No. 2004-188191 SUMMARY OF THE INVENTION [0010] The present invention has been made in view of the above-described problems. Therefore it is an object of the present invention to provide a golf club shaft that is lightweight and has a proper degree of flexibility and strength. [0011] To achieve the object, the present invention provides a golf club shaft composed of a laminate of prepregs each containing a matrix resin and reinforcing fibers impregnated with the matrix resin. The matrix resin of at least one of the prepregs contains a fullerene or/and a fullerene compound. [0012] The fullerene is a carbon allotrope having a three-dimensional hollow spherical structure closed with covalent bonds of sp2 carbon atoms. As the molecular structure of the fullerene, carbon atoms construct five-membered rings and six-membered rings, thus constructing a polyhedron. Representative fullerene is soccer ball-shaped C60 composed of 60 carbon atoms constructing 12 five-membered rings and 20 six-membered rings. The C60 is inexpensive, can be mass-produced, and is physically stable. In addition to C60, it is possible to use C70, C74, C76, C78, C80, C84, C82, and C90. These fullerenes can be used singly or in combination. [0013] As the fullerene compound, it is possible to use halogen-introduced C60Fn (n=30 through 52), C60C124, C60Brn (n=6, 8, 24), hydroxyl group-introduced C60(OH)24, hydrogen-added C60H24, a fullerene compound composed of the fullerene and metal such as Na, K, Rb or Cs doped in the crystal of the fullerene. [0014] By mixing the fullerene or/and the fullerene compound with the matrix resin of the prepreg composing the shaft, it is possible to restrain an increase of the weight of the shaft and the rigidity thereof and yet enhance the bending modulus of elasticity and strength thereof. [0015] This is because the hollow spherical fullerene and fullerene compound absorb a breaking energy, and in addition the fullerene and the resin combine with each other to form a firm crosslinking structure. Further the spherical fullerene is higher than the above-described cylindrical carbon nano-tube in its fluidity and dispersibility. Thus the fiber reinforced resin containing the hollow spherical fullerene has little variations in its strength. [0016] As the fullerene to be used in the present invention, C60, C70, and C80 soluble in an organic solvent can be preferably used. To uniformly disperse the fullerene in the matrix resin, it is preferable to dissolve and disperse the fullerene and a monomer of the matrix resin in the organic solvent and evaporate the organic solvent by an evaporator. [0017] After the fullerene is added to the matrix resin, it is preferable to knead them with a kneader, a three-roll or a biaxial extruder to disperse the fullerene in the matrix resin by utilizing a shear force. [0018] To enhance the dispersibility of the fullerene, it is preferable to chemically treat the surface thereof with a surface-active agent such as polyoxyethylene lauryl ether. [0019] It is possible to use the fullerene compound formed by bonding the fullerene such as C60, C70, and C80 with a functional group such as a hydroxyl group or metal atoms. In this case, it is possible to chemically bond the resin of the fiber reinforced resin or the surface of the reinforcing fiber with the functional group of the fullerene. Such a fullerene compound has improved affinity for the resin of the fiber reinforced resin and is hence capable of mixing with the resin to a high extent. [0020] As the size of the fullerene or/and the fullerene compound to be added to the matrix resin, it is favorable that the average diameter of molecules thereof are not less than 0.6 nm nor more than 3.5 nm. The fullerene having an average diameter of less than 0.6 nm is theoretically present but it is very difficult to collect or produce it. Further the fullerene having an average diameter of less than 0.6 nm has a small area of contact between it and the matrix resin of the fiber reinforced resin. Consequently a weak bonding occurs between the fullerene and the matrix resin. Thereby the shaft has a low strength increase rate. When the average diameter of molecules of the fullerene or/and the fullerene compound are more than 3.5 nm, the molecules of the fullerene are very large. Thereby the fullerene has a low degree of dispersibility in the matrix resin of the fiber reinforced resin. Consequently a weak bonding occurs between the matrix resin and the fullerene and the fullerene compound. Thereby the shaft has a weak strength. The lower limit of the average diameter of the molecules of the fullerene or/and the fullerene compound is set to more favorably 0.7 nm and most favorably 0.75 nm. The upper limit of the average diameter of the molecules thereof is favorably 3.2 nm and most favorably 2.8 nm. [0021] It is favorable that the length of the prepreg containing the fullerene or/and the fullerene compound (hereinafter often referred to as fullerene-containing prepreg) is set to not less than 2% nor more than 90% of the full length of the shaft. If the length of the fullerene-containing prepreg is less than 2%, the shaft has a small fullerene-containing region. Thus the length of the fullerene-containing prepreg is insufficient for improving the strength of the shaft. The length of the fullerene-containing prepreg is set to more favorably not less than 4% and most favorably not less than 6%. To improve the strength of the shaft, it is effective to widen the region in which the fullerene-containing prepreg is disposed. In this case, the shaft is expensive because the fullerene is very expensive. Therefore the length of the fullerene-containing prepreg is not more than 90% and more favorably not more than 80%. The fullerene-containing prepreg may be disposed over the full length of the shaft. Continue reading about Golf club shaft... Full patent description for Golf club shaft Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Golf club shaft patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Golf club shaft or other areas of interest. ### Previous Patent Application: Handle structure for ball striking equipments Next Patent Application: Golf club head and golf club Industry Class: Games using tangible projectile ### FreshPatents.com Support Thank you for viewing the Golf club shaft patent info. 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